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RK 9872

Phase monitor

RK 9872


Nominal voltage

Approvals and Markings


  • 0065075
  • RK9872.11 3/N AC400/230V 50/60HZ
The space saving phase monitor RK9872/800 from the Varimeter family monitors under- and... more

Product description

The space saving phase monitor RK9872/800 from the Varimeter family monitors under- and overvoltage as well as phase sequence in 3-phase systems. The response values are fixed. When connecting the measuring voltage to the inputs L1-L2-L3 and fault free system the relay switches on. When the measuring voltage is connected the unit checks a clockwise phase sequence. If this is not the case the yellow LED flashes. The output relay will not energise. After detection of under- or overvoltage on one or more phases for more the 5 sec. the relay switches off. The relay stays off for at least 2 seconds. The phase monitor measures the arithmetic mean value of the 3 phases against neutral.

Technical specifications

Measuring range max.: 400 V
Standard measuring range: 3/N AC 400/230 V
1- / 3-phase: 3
Output contacts: 1 C/O contact
Width: 17,5 mm
Enclosure design: Distribution board
Type: RK 9872


  • Reliability monitoring of 3- or 1-phase voltage systems on:
    - Undervoltage
    - Overvoltage
    - Phase sequence (at 3-phase voltage system)
  • Fast fault location
  • Preventive maintenance
  • Space saving


  • According to IEC/EN 60255-1
  • Detection of under-/overvoltage and phase sequence in 3-phase voltage systems
  • Without separate auxiliary voltage
  • LED-Indication for operation voltage and contact position
  • De-energized on trip
  • With fixed response value for undervoltage
  • With fixed response value for overvoltage
  • Width: 17,5 mm